Display device with pixel shift on screen

ABSTRACT

According to one embodiment, a display device includes a display unit configured to display an image for right eye and an image for left eye. Resolution of the display unit is P pixels or more per inch. Pixel shift of the image for right eye and the image for left eye displayed on the display unit is 0.021×P pixels or less and one pixel or more.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2017-009471, filed Jan. 23, 2017, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a display device.

BACKGROUND

A conventional three-dimensional display device makes an image for righteye and an image for left eye incident on right and left eyes of anobserver and urges the observer to recognize a three-dimensional image.

According to the conventional three-dimensional display device, theobserver needs to stay at a predetermined position to make the image forright eye incident on the right and the image for left eye incident onthe eye of the observer. If the observer moves to a position other thanthe predetermined position, at least a part of the image for right eyeis made incident on the left eye, at least a part of the image for lefteye is made incident on the right eye, and image quality to be observedby the observer may be degraded.

SUMMARY

The present application generally relates to a display device displayinga high quality image.

According to the embodiment, a display device includes a display unitconfigured to display an image for right eye and an image for left eye.Resolution of the display unit is P pixels or more per inch. Pixel shiftof the image for right eye and the image for left eye displayed on thedisplay unit is 0.021×P pixels or less and one pixel or more.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, and 1C illustrate an example of three-dimensional displayin parallax barrier system.

FIGS. 2A, 2B, and 2C illustrate an example of three-dimensional displayin lenticular lens system.

FIG. 3 is a graph showing an example of a relationship between a pixeldensity and sensation of realness.

FIG. 4 illustrates an example of pixel shift between the image for righteye and the image for left eye.

FIGS. 5A, 5B, and 5C illustrate an example of a prism filter used in thedisplay device according to the embodiment.

FIGS. 6A and 6B illustrate an example of situations of supplying a pixelsignal to each line of a display panel comprising the prism filter shownin FIG. 5A.

FIGS. 7A and 7B illustrate another example of the prism filter used inthe display device according to the embodiment.

FIGS. 8A and 8B illustrate an example of design of the prism filtershown in FIG. 5A.

FIG. 9 illustrate an example of design of the prism filter shown in FIG.5A.

FIGS. 10A, 10B, and 10C illustrate yet another example of the prismfilter used in the display device according to the embodiment.

FIGS. 11A and 11B illustrate an example of sub-pixel alignment and anexample of a prism filter in the display device according to theembodiment.

FIG. 12 is a block diagram showing a basic configuration of the displaydevice according to the embodiment.

FIG. 13 is a block diagram showing a specific configuration of thedisplay device according to the embodiment.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to theaccompanying drawings.

The disclosure is merely an example and is not limited by contentsdescribed in the embodiments described below. Modification which iseasily conceivable by a person of ordinary skill in the art comes withinthe scope of the disclosure. In order to make the description clearer,the sizes, shapes and the like of the respective parts may be changedand illustrated schematically in the drawings as compared with those inan accurate representation. Constituent elements corresponding to eachother in a plurality of drawings are denoted by like reference numeralsand their detailed descriptions may be omitted unless necessary.

A liquid crystal display device will be explained as an example of thedisplay device in the following descriptions. The embodiments are notlimited to a liquid crystal display device but may be the other displaydevice such as an organic EL device or a field emission display (FED).In addition, the display device according to the embodiment is notlimited to a display device of a specific product, but can be applied tovarious products. Application examples can be implemented unlimitedlybut several application examples will be explained here.

One of the application examples is a display device for automobile. Anautomobile includes an instrumental panel attached to a dashboard infront of a driver's seat and a display panel for car navigationgenerally mounted in front of a middle part between the driver's seatand a passenger seat. The display device according to the embodiment canbe applied to these panels. The instrument panel displays meters such asa speedometer, a tachometer and a warning lamp and alarms (for driverassistance, autonomous driving, and the like). Furthermore, theinstrument panel can also display simple car navigation images (forexample, navigation of only corners for turning right or turning left,and the like) in free space on the screen. Furthermore, the displaypanel for car navigation can also be used as a rearview monitor. If athree-dimensional image is displayed on these display modules,improvement of visibility of the meters, alarms, and navigation screen,and promotion of safe driving are expected. If not only the driver, butalso the passenger in the passenger seat recognize the three-dimensionalimage, they can compensate for a driver's mistake and the like. Thedisplay panel can be applied to instrument panels and the like for notonly the automobile, but also all moving bodies such as motorcycles,trains, airplanes, and ships.

The other application example is a display device for medical use. Aplurality of doctors conduct diagnoses and operations while capturingthe inside of the body and affected parts and watching the capturedimages on a display device in endoscopic diagnoses and abdominaloperations. If these images are three-dimensional images, fine partssurrounding the affected parts are clarified and the improvement ofefficiency in endoscope operations and surgery is expected.

A further application example is a display device for amusement such asa game console, and the like.

[Three-Dimensional Image]

A three-dimensional image will be explained before explanation of aspecific example of the display device according to the embodiment.Examples of the three-dimensional image display mode include parallaxbarrier mode and lenticular mode. In either of the modes, an image of avisual field from the right eye, i.e., an image for right eye and animage of a visual field from the left eye, i.e., an image for left eyeare captured, and displayed alternately or simultaneously. The image forright eye and the image for left eye are thereby made incident on theright eye and the left eye, respectively. The observer is allowed torecognize the three-dimensional image.

In the parallax barrier mode, as shown in FIGS. 1A, 1B, and 1C, aparallax barrier 14 is disposed parallel to a display panel 12, at aposition between the display panel 12 and an observer 16. Plural narrowslits are provided in a longitudinal direction of the display screen, inthe parallax barrier 14. The slits may be aligned in a directionintersecting a parallax direction, a perpendicular direction. Theobserver 16 observes a display image on the display panel 12 through theslits of the parallax barrier 14. The image for right eye and the imagefor left eye to display a three-dimensional image are divided laterally(perpendicular direction) and an image for right eye I_(R) and an imagefor left eye I_(L) in a longitudinally strip shape are therebygenerated. An image formed by alternately arranging the image for righteye and the image for left eye in a strip shape is displayed on thedisplay panel 12. A cycle of the slits is set to be similar to a cycleof the images I_(L) and I_(R) in a strip shape as seen from the observer16 and an opening width of the slits is set to be similar to a width ofthe image for right eye I_(R) and an image for left eye I_(L) in a stripshape as seen from the observer 16. A distance between the parallaxbarrier 14 and the display panel 12 and a distance between the parallaxbarrier 14 and the observer 16 are set such that the only image forright eye I_(R) displayed on the display panel 12 is made incident onthe right eye of the observer 16 and the only image for left eye I_(L)displayed on the display panel 12 is made incident on the left eye ofthe observer 16. For this reason, when the observer 16 is presented at apredetermined position remote from the display panel 12 in apredetermined distance, in front of the display panel 12, the image forright eye I_(R) and the image for left eye I_(L) alone are made incidenton the right eye and left eye of the observer 16, respectively, as shownin FIG. 1A. The observer 16 can recognize the depth and also recognizethe three-dimensional image by intracerebrally processing binoculardisparity indicating a difference between the image for right eye I_(R)reflected on retina of the right eye and the image for left eye I_(L)reflected on retina of the left eye. Binocular disparity is often calledbinocular parallax. Binocular parallax often indicates parallax which isdetermined by the target and the eyeball position and does not depend onthe direction of the line of sight but, in the present specification,binocular disparity is called binocular parallax.

When the position of the observer 16 moves from a predeterminedposition, for example, shifted from the position shown in FIG. 1A in alateral direction parallel to the display panel 12 as shown in FIG. 1B,a part of the image for right eye I_(R) and a part of the image for lefteye I_(L) are made incident on the right eye of the observer 16 whilethe remaining part of the image for right eye I_(R) and the remainingpart of the image for left eye I_(L) are made incident on the left eyeof the observer 16. For this reason, the observer 16 recognizes anindistinct or blurred two-dimensional image but cannot recognize athree-dimensional image. Thus, a situation in which at least a part ofthe image for right eye I_(R) is made incident on the left eye and atleast a part of the image for left eye I_(L) is made incident on theright eye is called crosstalk. The display quality of thethree-dimensional display is degraded as the rate of the crosstalk islarger. In other words, an observer at a predetermined position canrecognize a three-dimensional image, but the passenger in the passengerseat, other doctor, and the like watching the same screen cannotrecognize the three-dimensional image and can recognize the onlyindistinct or blurred two-dimensional image.

Furthermore, if the observer 16 moves and the crosstalk increases, theimage for right eye I_(R) alone is made incident on the left eye of theobserver 16 and the image for left eye I_(L) alone is made incident onthe right eye of the observer 16, oppositely to the state shown in FIG.1A, as shown in, for example, FIG. 1C. In this case, since the imagesdifferent in light of sight are observed by the right and left eyes, theimages are seen three-dimensionally but depth positions of two objectsare opposed, i.e., pseudo stereoscopy. The observer's movement is notlimited to shifting in the direction parallel to the display panel 12but indicates movement in a direction intersecting the display panel 12and movement in an oblique direction.

In the lenticular mode, as shown in FIGS. 2A, 2B, and 2C, longitudinallyextending semi-cylindrical lenses 18 called lenticular lenses arearranged laterally and installed on the surface of the display panel 12instead of the parallax barriers. Each of the lenticular lenses 18 isprovided to correspond to a perpendicular pixel string (column) whichdisplays a pair of the image for right eye I_(R) and the image for lefteye I_(L) in a strip shape. A focal position of the lenticular lens 18exists on the image display surface of the display panel 12. A lightemission direction of the lenticular lens 18 is set such that the onlyimage for right eye I_(R) displayed on the display panel 12 is madeincident on the right eye of the observer 16 and the only image for lefteye I_(L) displayed on the display panel 12 is made incident on the lefteye of the observer 16. For this reason, when the observer 16 ispresented at a predetermined position remote from the display panel 12in a predetermined distance, in front of the display panel 12, the imagefor right eye I_(R) and the image for left eye I_(L) alone are madeincident on the right eye and left eye of the observer 16, respectively,as shown in FIG. 2A. The observer 16 can recognize the three-dimensionalimage, based on the image for right eye I_(R) and the image for left eyeI_(L) different in visual field.

When the observer 16 moves from a predetermined position, for example,shifted from the position shown in FIG. 2A in a lateral directionparallel to the display panel 12 as shown in FIG. 2B, a part of theimage for right eye I_(R) and a part of the image for left eye I_(L) aremade incident on the right eye of the observer 16 while the remainingpart of the image for right eye I_(R) and the remaining part of theimage for left eye I_(L) are made incident on the left eye of theobserver 16. For this reason, the observer 16 recognizes an indistinctor blurred two-dimensional image but cannot recognize athree-dimensional image.

Furthermore, if the observer 16 moves and the crosstalk increases, theimage for right eye I_(R) alone is made incident on the left eye of theobserver 16 and the image for left eye I_(L) alone is made incident onthe right eye of the observer 16, oppositely to the state shown in FIG.2A, as shown in, for example, FIG. 2C and pseudo stereoscopy is caused.The observer's displacement is not limited to shifting in the directionparallel to the display panel 12 but indicates movement in a directionintersecting the display panel 12 and movement in an oblique direction.

[Pictorial Cues]

The binocular parallax is not the only factor which enables a human torecognize the image depth and recognize a three-dimensional image. Ingeneral, it is well known that a human recognizes an image as athree-dimensional image with total actions of (1) binocular parallax,(2) motion parallax (using a remote object moving slowly and a closeobject moving fast), and (3) pictorial cues (shading, perspective, sizeratio, sensation of realness, and the like). For this reason, even ifbinocular parallax is small, the three-dimensional image can berecognized with motion parallax or pictorial cues. According to theembodiment, the three-dimensional image can be recognized with pictorialcues and the image for right eye and the image for left eye having smallbinocular parallax.

When the observer 16 moves from the predetermined position as shown inFIG. 1B and FIG. 2B, the observer recognizes not the three-dimensionalimage, but two images, i.e., the image for right eye and the image forleft eye. If the binocular parallax of the image for right eye and theimage for left eye is small, the observer at the displaced positions asshown in FIG. 1B and FIG. 2B recognizes the two-dimensional image withinconspicuous blur as compared with the case shown in FIG. 1B and FIG.2B. If the pictorial cues are present, even if the position of theobserver 16 greatly moves and the image for right eye I_(R) alone ismade incident on the left eye of the observer 16 and the image for lefteye I_(L) alone is made incident on the right eye of the observer 16, asshown in FIG. 1C and FIG. 2C, the observer can recognize a distinct orunblurred two-dimensional image without recognizing positions of theobjects oppositely (pseudo stereoscopy). In addition, pseudo stereoscopyhardly occurs as the binocular parallax is smaller.

An example of pictorial cues will be explained. Sensation of realnesswill be explained as an example. Sensation of realness is one ofpsychophysical effects of vision and indicates a degree of feeling ofwatching a real object. Sensation of realness is known as feelingrelated to spatial resolution (or pixel density) which is one of thevideo parameters. If the spatial resolution becomes high, the realobject and the video image cannot be distinguished from each other. Thespatial resolution indicates the number of pairs of black and whitepixels that can be seen at each degree of the viewing angle in thehorizontal direction, and is defined as cycles per degree (cpd). Theupper limit of the pixel density at which a person having sight of 1.0can sense the pixel structure is 30 cpd (sixty pixels per degree ofvisual field). As shown in FIG. 3, experiment results (average values)obtained by presenting pairs of video of six pixel densities of 26 cpd,30 cpd, 40 cpd, 50 cpd, 80 cpd, and 155 cpd and the subject (realobject) to a number of evaluators and urging the evaluators to determinewhich looks more similar to the real thing are known. FIG. 3 is shown inNHK Science & Technology Research Laboratories R&D No. 137/2013.1 (FIG.2).

It can be understood from this result that on any object, sensation ofrealness is improved if the pixel density is 30 cpd or more andsensation of realness is approximately saturated if the pixel density is60 cpd or more. For this reason, it can be understood that the pixeldensity of the display device needs to be 60 cpd or more to obtainsensation of realness (an example of the pictorial cues) which enablesstereoscopic vision.

Since the pixel density is the observer's characteristic, this isconverted into the resolution (pixels per inch; ppi) which is thecharacteristic of the display device. In a vehicle-mounted displaydevice, a display device for medical use or the like, a visual range tothe display screen is approximately 60 cm. The lower limit of theresolution (ppi) of the display device to achieve the pixel density of60 cpd or more in a visual range of 60 cm can be obtained in a mannerexplained below.

A width of a pixel necessary for 60 cpd in the visual range of 60 cm isa distance on a circumference having a radius of 60 cm about theobserver 16, and can be obtained in a manner explained below withtrigonometric function.Width of pixel=[tan( 1/60 cpd)×60 cm/2] cm

The number of pixels per cm can be obtained from a reciprocal of thepixel width.Number of pixels per cm=1/[tan( 1/60 cpd)×60 cm/2]

Since 1 inch is equivalent to 2.54 cm, the number of pixels per inch(ppi) can be obtained in a manner explained below.Number of pixels per cm=1/[tan( 1/60 cpd)×60 cm/2]×2.54≈291.0

For this reason, in the embodiment, the resolution of the display deviceis set to 300 ppi or more to achieve the pixel density of 60 cpd or morein the visual range of 60 cm. The resolution by which sensation ofrealness can be obtained is varied in accordance with the visual range.The resolution necessary to obtain sensation of realness becomes largeif the observer and the display device are close to each other and thevisual range is short and, oppositely, the resolution necessary toobtain sensation of realness becomes small if the observer and thedisplay device are remote from each other and the visual range is long.As for a color image, the resolution is not the resolution of, forexample, each of red (R), green (G), and blue (B) sub-pixels, but theresolution of pixels including sub-pixels.

[Binocular Parallax]

Next, binocular parallax which is a factor of three-dimensional imagerecognition together with the pictorial cues (sensation of realness)will be explained with reference to FIG. 4. When the observer watchesobject Oa with the eyes, an image of object Oa is generated in thecenters of the binocular retinae. At this time, an image of object Obfarther than object Oa (or a closer object not shown) is formed atdifferent positions on the binocular retinae (not the centers of thebinocular retinae). The difference between the positions on the retinaeof images of objects Oa and Ob (also called pixel shift of image) is thebinocular parallax and the depth clue.

Since sensation of realness is improved as the resolution becomes 300ppi or more as explained above, the pictorial cues as the elements withwhich the object image can be visually recognized as three-dimensionalimage. For this reason, it was recognized that the three-dimensionalobject image can be visually recognized even if binocular parallax δ ismade smaller. More specifically, if the resolution is set to 300 ppi inthe visual range of 60 cm, the observer can recognize thethree-dimensional image with binocular parallax δ of 4.3 arc min orless. Furthermore, if binocular parallax δ is 3 arc min or less, theproblem of pseudo stereoscopy does not occur and the observer canrecognize the three-dimensional image. If the resolution is set to 300ppi with binocular parallax δ of 4.3 arc min or less in the visual rangeof 60 cm, degradation of the image quality is not recognized and theimage is recognized as a general two-dimensional image even if crosstalkoccurs. Furthermore, by setting binocular parallax δ to 3 arc min orless, the deterioration of image quality due to pseudo stereoscopy canbe prevented and a clear two-dimensional image can be recognized whenobserved at a position of the pseudo stereoscopy.

For this reason, if the display device of the embodiment is applied to avehicle, a three-dimensional image is recognized in the driver's seatwhile a distinct or unblurred two-dimensional image is recognized in thepassenger seat. By changing the arrangement of the parallax barrier orlenticular lens and changing the image for right eye and the image forleft eye, a three-dimensional image can be recognized in the passengerseat while a distinct or unblurred two-dimensional image can berecognized in the driver's seat, oppositely to the above case. If thedisplay device according to the embodiment is applied to a medical use,a three-dimensional image is recognized in the main observer while adesirable two-dimensional image is recognized by other observers. Inthis case, the position of the main observer for the display device isnot limited to a position in front of the display device, but may be apredetermined position displaced to the side surface. According to theembodiment, the position of the main observer recognizing athree-dimensional image can be set freely, and the other observers atthe other positions can recognize a distinct or unblurredtwo-dimensional image.

If binocular parallax δ is 3 arc min, the width of shift DISP betweenthe image for right eye and the image for left eye on the screen is asfollows.

DISP = E − tan [arctan (E/2D) − δ/2] × 2D = 0.000874 × D  (m)DISP  is  0.000874 × 0.6  (m)  where  D = 0.6  m.

The length of a pixel on the screen of the display device having theresolution of 300 ppi is 2.54/300=0.08467 mm. It can be thereforeunderstood that if the display device having the resolution of 300 ppiis used, the pixel shift of the images on the screen is(DIPS/0.08467)×1000≈6.19 (pixels) to make the three-dimensional imagerecognizable. The pixel shift which makes the three-dimensional imagerecognizable is varied in accordance with the resolution and becomeslarge as the resolution is made higher. For this reason, if the displaydevice having the resolution of 300 ppi is used, the pixel shift of theimages on the screen which makes the three-dimensional imagerecognizable is 6.19 pixels. If the resolution becomes 300 ppi or more,the pixel shift which makes the three-dimensional image recognizablebecomes 6.19 pixels or more in proportion to the resolution.

In the embodiment, the three-dimensional image can be recognized bydisplaying the image for right eye and the image for left eye having thepixel shift on the display screen of 6.3 pixels (=0.021×300) larger than6.19 pixels, by using the display device having the resolution of 300ppi which is capable of obtaining sensation of realness in the visualrange of 60 cm. The three-dimensional image can be recognized at anappropriate place and the two-dimensional image can be recognized at theother place so that the embodiment is useful for a glasslessstereoscopic display. According to the embodiment, the resolution of thedisplay unit is P pixels or more per inch, and the pixel shift betweenthe image for right eye and the image for left eye displayed on thedisplay unit is 0.021×P pixels or less. In contrast, the lower limitwhich makes the image recognizable as a stereoscopic image is about 2arc sec. Thus, the lower limit of the pixel shift is set to 0.00023×Ppixels. Therefore, the lower limit of the pixel shift in a case wherethe resolution is 300 ppi is calculated at 0.07 (0.00023*300 pixels) ormore, which is rounded up to 1 pixel.

[Prism Filter]

The lenticular lens (FIGS. 2A, 2B, and 2C) and the parallax barrier(FIGS. 1A, 1B, and 1C) are used as an example of the optical element formaking the image for right eye incident on the right eye and making theimage for left eye incident on the left eye in the above explanations.Another example of the optical element will be explained below. Forexample, even if a prism filter in which a prism is arranged for each ofsub-pixels of a plurality of color components, for example, R, G, and Bsub-pixels constituting one pixel is used, the image for right eye canbe made incident on the right eye and the image for left eye can be madeincident on the left eye.

FIG. 5A shows an example of arranging prism filters 24 a and 24 bdifferent in light emitting direction in each horizontal line (rowdirection) of the display unit. FIG. 5A shows two horizontal linesalone, but the prism filters 24 a and 24 b in the two lines are disposedrepeatedly. For example, the prism filter 24 a which emits the lightshown in FIG. 5B in the direction of the right eye is attached to theodd-numbered line of the display panel 22 while the prism filter 24 bwhich emits the light shown in FIG. 5C in the direction of the left eyeis attached to the even-numbered line of the display panel 22. The prismfilter 24 a is composed of a number of prisms, and the prisms arearranged to correspond to R, G, and B sub-pixels. Since the parallaxbarrier (slits) and the lenticular lens are arranged in the longitudinaldirection (vertical direction), the image for right eye and the imagefor left eye are divided in the lateral direction (horizontaldirection), the image for right eye I_(R) and image for left eye I_(L)shaped in a longitudinal strip (vertical strip) are alternately arrangedin the lateral direction (horizontal direction) to display one image.However, when the prism filters 24 a and 24 b shown in FIGS. 5A-5C areused, the image for right eye and the image for left eye are divided inthe lateral direction (horizontal direction), and the image for righteye and image for left eye shaped in a lateral strip (horizontal strip)are alternately arranged in the longitudinal direction (verticaldirection) to display one image.

For example, if the horizontal lines of one screen are N lines, each ofthe image for right eye and the image for left eye is divided in thelateral direction (horizontal direction) into N lateral strips(horizontal strips), which are partial images of N horizontal lines asshown in FIG. 6A. As for the image for right eye, the partial images inthe odd-numbered rows are displayed in odd-numbered lines L1, L3, . . .of the display panel 22 and the partial images of the even-numbered rowsare not displayed. As for the image for left eye, the partial images inthe even-numbered rows are displayed in even-numbered lines L2, L4, . .. of the display panel 22 and the partial images of the odd-numberedrows are not displayed.

Alternatively, each of the image for right eye and the image for lefteye is divided in the lateral direction (horizontal direction) into(N/2) pieces, which are partial images of (N/2) horizontal lines asshown in FIG. 6B. The partial image in the first row of the image forright eye is displayed in the first horizontal line L1 of the displaypanel 22 while the partial image in the first row of the image for lefteye is displayed in the second horizontal line L2 of the display panel22. Similarly, the partial image in the second row of the image forright eye is displayed in the third horizontal line L3 of the displaypanel 22 while the partial image in the second row of the image for lefteye is displayed in the fourth horizontal line L4 of the display panel22.

Thus, since the light emitting directions of the image for right eye andthe image for left eye displayed on the display panel 22 are controlledby the prism filters 24 a and 24 b, the image for right eye and theimage for left eye are made incident on the right eye and the left eye,respectively, and the observer can recognize the three-dimensionalimage.

A second example using the prism filter is shown in FIGS. 7A-7B. A prismfilter 34 configured to differentiate the light emission direction fornot each horizontal line, but each vertical line (column direction) isattached to the display panel 32 as shown in FIG. 7A. One vertical lineof the prism filter 34 corresponds to one pixel, and one pixel iscomposed of sub-pixels of R, G, and B. For example, the prism filter 34is configured to emit the light to the right eye direction in theodd-numbered columns and to emit the light to the left eye direction inthe even-numbered columns. FIG. 7B is a cross-sectional view showing thehorizontal line of the display panel 32. One pixel is composed of threesub-pixels of R, G, and B on the display panel 32, similarly to the caseshown in FIGS. 5A-5C.

In the example shown in FIGS. 5A-5C, the image for right eye, and theimage for left eye are divided in the horizontal direction, the partialimages of the horizontal lines are generated, and the partial images forright eye and the partial images for left eye are selectively displayedin each display row but, in the example shown in FIGS. 7A-7B, the imagefor right eye and the image for left eye are divided in the verticaldirection, the partial images of the vertical lines are generated, andthe partial images for right eye and the partial images for left eye areselectively displayed in each column.

Since the refractive index n of resin or glass which is the material ofthe prism filter 34 is varied in accordance with the wavelength oflight, the prism is provided for not each sub-pixel, but every threesub-pixels as shown in FIGS. 7A-7B and the prism shapes are varied inaccordance with the refractive index. The prism filter 34 correspondingto one pixel (three sub-pixels) has the same shape for convenience inFIG. 7A but, actually, the shape of the prism filter 34 is varied foreach sub-pixel as shown in FIG. 7B. If the shapes of the prisms of threesub-pixels of R, G, and B are the same, the emission angles of R, G, andB light beams are different. Thus, the positions of the pixels emittingthe light beams incident on the observer is shifted, and the imagequality is degraded. If the shape of the prism filter 34 is designed foreach sub-pixel in accordance with the refractive index, the prism shapecan compensate for degradation in image quality. The shapes of the prismfilters 24 a and 24 b shown in FIGS. 5A-5C can also be designed for eachsub-pixel.

A method of obtaining refraction face angles (angles made betweenrefraction faces emitting the light and the display panel 32) ϕ_(R),ϕ_(G), and ϕ_(B) of the prism filters 24 a, 24 b, and 34 for therespective R, G, and B sub-pixels shown in FIGS. 5A-5C and FIGS. 7A-7Bwill be explained with reference to FIGS. 8A-8B. FIG. 8A shows a prismfilter of even-numbered columns which emit the light in the left eyedirection while FIG. 8B shows a prism filter of odd-numbered columnswhich emit the light in the right eye direction. The prism filters 24 a,24 b, and 34 are formed of resin, for example, polymethyl methacrylateresin. When the refractive indices of polymethyl methacrylate resin toR, G, and B light beams are denoted by n_(R), n_(G), and n_(B), thelight emission angle θ_(T) of R, G, and B light beams is represented asfollows.arcsin(n _(C) sin(ϕ_(C)))−ϕ_(C)=θ_(T)

Refractive index n_(C) is composed of refractive indices n_(R), n_(G),and n_(B) of the respective wavelengths of light, which aren_(R)=1.4880, n_(G)=1.4913, and n_(B)=1.4974. Refraction face angleϕ_(C) is composed of ϕ_(R), ϕ_(G), and ϕ_(B). Light emission angle θ_(T)is composed of θ_(TL) and θ_(TR) (each varied for each color).

When refractive index n_(C) and light emission angle θ_(T) of polymethylmethacrylate resin are determined, refraction face angles ϕ_(R), ϕ_(G),and ϕ_(B) of the prisms of the respective R, G, and B sub-pixels areobtained. These refraction face angles are obtained with wavelengthsλ_(R)=655 nm, λ_(G)=590 nm, and λ_(GB)=485 nm, respectively.

FIG. 9 shows the light emission angle θ_(T) obtained when a 55-inch(horizontal size of screen: 1.218 m) display is observed in the visualrange of 60 cm. If it is assumed that the display can be approached inup to 60 cm and can be seen from the surrounding at up to 80 degrees,the barycenter of emission angle θ is 17.3 degrees which is an averageof 80 degrees and −45.4 degrees.

The prism filters shown in FIGS. 5A-5C and FIGS. 7A-7B achieve the sameadvantage on recognition of the three-dimensional image. When the prismfilters shown in FIGS. 5A-5C and FIGS. 7A-7B are compared in view offacility of manufacturing, a mold of the prism filter shown in FIGS.7A-7B in which the shape is arranged in the vertical direction can beprocessed slightly more easily and its manufacturing costs are lower.

If the refraction face angles of the prisms of the R, G, and Bsub-pixels are set to be the same without considering the refractiveindex of each wavelength, the emission angles of R, G, and B light beamsare shifted and the positions of the pixels emitting the light beamsreaching the observer's retinae of the R, G, and B color componentimages, is shifted. This amount of shift is calculated to approximately0.159315 degrees, based on the difference between the R and B emissionangles, by a prism of polymethyl methacrylate resin, when the refractionface angle ϕ is 15.7 degrees. For this reason, if 20-inch HD display(horizontal size of screen: 44.3 cm) is observed in a visual range of 60cm, the pixel position is shifted by 7.2 pixels on the display screenand the image quality is degraded. If the material of low wavelengthdispersion (small difference in refractive index for each wavelength) isselected as the resin of the prisms, the shift can be minimized orcanceled but the costs are increased by the material. If the refractionface angle ϕ is optimized for each of the R, G, and B sub-pixels andemission angles θ_(TL) and θ_(TLR) of the R, G, and B light beams areadjusted as shown in FIGS. 8A-8B and FIG. 9, the positions of the pixelsemitting the light beams reaching the observer's retinae, of the R, G,and B color component images, can be made the same by even using prismsof low cost resin.

[Sub-Pixel Alignment]

As explained above, one pixel of the display device is composed of threeR, G, and B sub-pixels and, generally, the three R, G, and B sub-pixels(or color filters) are aligned cyclically. The prisms corresponding toR, G, and B are different in refraction face angle, the refraction faceangle of the prism corresponding to R is the largest and the refractionface angle of the prism corresponding to B is the smallest. For thisreason, if the R, G, and B sub-pixels are aligned cyclically in thisorder, the refraction face angles of the prisms are repeatedly variedfor each of the sub-pixels as shown in FIG. 10A. Thus, manufacturing theprism filter having recesses and projections for each of the sub-pixelsmay be slightly difficult.

If the cycle of the alignment of the sub-pixels is set to a cycle of R,G, B, B, G, and R (two pixels) and is repeated, the manufacturing may befacilitated.

For example, as shown in FIG. 10B, the alignment of the sub-pixels of R,G, B, B, G, and R is defined as one cycle and repeated, and thethickness of each of the prisms corresponding to the R, G, and Bsub-pixels is increased by a predetermined amount, such that therefraction surface is substantially continuous in three continuoussub-pixels of R, G, and B and three continuous sub-pixels of B, G, andR. The predetermined amount for the R, G, and B sub-pixels is determinedsuch that the prism corresponding to the B sub-pixel is made thethickest and the prism corresponding to the R sub-pixel is made thethinnest. Thus, the refraction face angle of a prism filter 34A becomesapproximately constant for the sub-pixels of R, G, and B in the formerpart of one cycle, and also becomes approximately constant for thesub-pixels of B, G, and R in the latter part of one cycle. For thisreason, since the shape of the refraction surface of the prisms isvaried in units of six sub-pixels (two pixels) and the cycle ofirregularities is long, the prism filter 34A may be manufactured moreeasily than that shown in FIG. 10A. The perspective view of the prismfilter 34A shown in FIG. 10B is the same as FIG. 7A.

In FIG. 10C, the thickness of the prisms corresponding to the R, G, andB sub-pixels is the same as that in FIG. 10A, and the alignment of thesub-pixels is composed of a cycle of R, G, B, B, G, and R and isrepeated. Thus, since the shape of the refraction surface of the prismfilter 34B is varied in units of six sub-pixels and the thickness ofeach prism is approximately constant, the prism filter may bemanufactured more easily than that shown in FIG. 10A.

The above explanations are made on the assumption that each of thehorizontal lines of the display panels 22 and 32 is composed of threesub-pixels of R, G, and B for each pixel, the alignment of thesub-pixels has several modified examples, but the all the horizontallines are the same sub-pixel alignments.

FIG. 11A shows an example of alignment of the sub-pixels on the wholedisplay panel. The alignment of the sub-pixels in each horizontal lineis composed of a cycle of six sub-pixels of R, G, B, B, G, and R and isrepeated, similarly to that in FIGS. 10B-10C. For example, in the firstline, R, G, and B sub-pixels are aligned in this order from the left, inthe left pixel of two adjacent pixels, and B, G, and R sub-pixels arealigned in this order from the left, in the right pixel of two adjacentpixels. In the second horizontal line adjacent to the first horizontalline, the alignment of the sub-pixels is shifted by one sub-pixel. Inother words, the pixel in the second line located under the left pixelcomposed of the sub-pixels of R, G, and B in the first line is composedof the sub-pixels of R, R, and G, and the pixel in the second linelocated under the right pixel composed of the sub-pixels of B, G and Rin the first line is composed of the sub-pixels of B, B, and G. For thisreason, the sub-pixels of the same color are aligned obliquely from theupper left side to the lower right side.

FIG. 11B is a perspective view showing an example of a prism filter 34Cused in the display device shown in FIG. 11A. The prism filter 34C ofone horizontal line may comprise the configuration shown in FIG. 10B orFIG. 10C, and may be attached to the display device while shifted by onesub-pixel in each horizontal line. FIG. 11B shows an example of usingthe prism filter 34C in which each horizontal line is configured asshown in FIG. 10B. It may possible to configure the prism filter 34C inwhich each horizontal line is configured as shown in FIG. 10C. If thealignment of the sub-pixels is shifted in each line, interference of alongitudinal outline component and an emitted light component is avoidedand the image quality is improved. The direction of shifting the secondline with regard to the first line may be opposite to the direction ofFIGS. 11A-11B, and the shift amount may not be one sub-pixel, but aplurality of sub-pixels.

The alignment of the sub-pixels shown in FIGS. 5A-5C, FIGS. 7A-7B, andFIGS. 10A-10C, i.e., the alignment of the color filters is not onlyapplied to the display device in which the resolution to display theimage for right eye and the image for left eye is 300 ppi and the imagefor right eye and the image for left eye has the pixel shift of 6.19pixels. The alignment of the color filters can also be applied to ageneral display device of low resolution which executesthree-dimensional display based on the image for right eye and the imagefor left eye having large pixel shift.

[Circuit Configuration]

FIG. 12 is a block diagram showing an example of a basic configurationof the three-dimensional image display device. The display device iscomposed of a storage device 92, a controller 94, and a glasslessstereoscopic display 96. The glassless stereoscopic display 96 comprisesan optical system of making the image for right eye incident on theright eye and making the image for left eye incident on the left eye asshown in FIGS. 5A-5C, FIGS. 7A-7B, FIGS. 10A-10C, or FIGS. 11A-11B, andis composed of a liquid crystal display or organic EL display having theresolution of 300 ppi or more on an assumption that the images areobserved in the visual range of 60 cm. The image for right eye and theimage for left eye are input from a PC or camera to the display deviceand stored in the storage device 92. Examples of the image for right eyeand the image for left eye stored in the storage device 92 include theimages captured by a three-dimensional camera having small parallax orthree-dimensional images generated by a graphics controller of apersonal computer. An example of the latter may include an image of anautomobile's speedometer or the like. The pixel shift between the imagefor right eye and the image for left eye is 0.021×P pixels on thedisplay screen where the resolution of the display unit is P pixels. Thecontroller 94 drives each of the pixels of the glassless stereoscopicdisplay 96 such that the image for right eye and the image for left eyeare alternately arranged in the lateral direction (horizontal direction)as shown in FIGS. 5A-5C, or in the longitudinal direction (verticaldirection) as shown in FIGS. 7A-7B, FIGS. 10A-10C, or FIGS. 11A-11B.

FIG. 13 is a block diagram showing an example of a concrete example ofthe three-dimensional image display device. The display device includesa liquid crystal display panel 130 and a circuit board 106. The liquidcrystal display panel 130 includes a liquid crystal layer (not shown)sandwiched between the array substrate and the counter-substrate, adisplay unit DYP composed of a plurality of pixels arrayed in a matrix,and a backlight (not shown).

The display unit DYP includes a transparent insulating substrate (notshown), pixel electrodes arrayed in a matrix so as to correspond to therespective display pixels on the transparent insulating substrate.Scanning lines GL are arranged in rows and signal lines SL are arrangedin columns. Pixel electrodes PE and pixel switches SW are arranged nearpositions at which the scanning lines GL and the signal lines SLintersect. Scanning line drive circuits YD and signal line drivecircuits XD are arranged in the surrounding of the display unit DYP.

A color filter composed of R, G, and B color components shown in FIGS.5A-5C, FIGS. 7A-7B, FIGS. 10A-10C, or FIGS. 11A-11B is provided on thetransparent insulating substrate, though not illustrated in FIG. 13.Each of the color components of the color filter corresponds to a pixelelectrode PE. One pixel electrode PE corresponds to a sub-pixel andthree pixel electrodes PE correspond to one pixel. The pixel resolutionof the display unit DYP is 300 ppi or more.

The lenticular lens 18 shown in FIGS. 2A-2C or the prism filter shown inFIGS. 5A-5C, FIGS. 7A-7B, FIGS. 10A-10C, or FIGS. 11A-11B is provided tofacilitate recognition of the three-dimensional image, though notillustrated in the drawing. Alternatively, the parallax barrier 14 maybe provided between the display device and the observer to facilitaterecognition of the three-dimensional image, as shown in FIGS. 1A-1C.

The pixel switch SW includes a thin film transistor including apolysilicone or amorphous semiconductor layer. A gate electrode of thepixel switch SW is electrically connected to (or formed integrally with)the corresponding scanning line GL. A source electrode of the pixelswitch SW is electrically connected to (or formed integrally with) thecorresponding signal line SL. A drain electrode of the pixel switch SWis electrically connected to (or formed integrally with) thecorresponding pixel electrode PE.

The scanning line drive circuits YD are disposed on both sides of thedisplay unit DYP in a direction of the scanning lines GL and areelectrically connected to the scanning lines GL. Each of the scanningline drive circuits YD sequentially outputs drive signals to thescanning lines GL, based on a vertical synchronization signal and aclock signal received from the circuit board 106.

The signal line drive circuits XD are disposed on both sides of thedisplay unit DYP in a direction of the signal lines SL and areelectrically connected to the signal lines SL. Each of the signal linedrive circuits XD outputs video signals received from the circuit board106 to the signal lines SL in parallel.

An end of each of flexible substrates FC is electrically connected to anend portion of the liquid crystal display panel 130. The circuit board106 is electrically connected to the other end of the flexible substrateFC. The circuit board 106 includes a buffer memory 108, multiplexers(MUXs) 120, a D/A converter (DAC) 114, an A/D converter (ADC) 112, aninterface (I/F) 110 executing signal transmission and reception with anexternal image source 104 for generating an image for right eye and animage for left eye, and a controller 118.

The image for right eye in the visual field from the right eye and theimage for left eye in the visual field from the left eye are captured bya stereo camera 102. The image source 104 receives an image signal forright eye and an image signal for left eye from the stereo camera 102,divides the image for right eye and the image for left eye in thehorizontal direction or the vertical direction, generates partial imagesfor right eye and partial images for left eye in the horizontal line orthe vertical line, and outputs the image obtained by alternatelycombining the partial images for right eye and the partial images forleft eye. The pixel shift between the image for right eye and the imagefor left eye is 0.021×P pixels on the display screen. P represents theresolution of the display device (number of pixels per inch). The imagefor right eye and the image for left eye do not necessarily need to beinput to the image source 104 but may be supplied from the server, thehost device, or the like to the image source 104.

An output image signal of the image source 104 is written to the buffermemory 108 via the interface (I/F) 110. The buffer memory 108 iscomposed of, for example, a volatile semiconductor memory capable ofstoring an image signal of several frames. The image signal is read fromthe buffer memory 108 in each frame in accordance with the display cycleof the display unit DYP and is supplied to the controller 118.

The controller 118 generates the synchronization signal from the imagesignal, outputs the vertical synchronization signal to the scanning linedrive circuits YD, and outputs the horizontal synchronization signal andthe image signal to the signal line drive circuits XD. The scanning linedrive circuits YD and the signal line drive circuits XD drive each ofthe pixel switches SW, based on the image signal and the synchronizationsignals, and execute display drive such that a gradation voltage of apotential line selected from plural potential lines is supplied to thecorresponding liquid crystal layer via each of the pixel electrodes PE.

The scanning line drive circuits YD select the pixel electrodes PE to bedriven in linear sequence (i.e., execute linear sequence scanning), bysequentially selecting the pixels for each of the horizontal lines withthe scanning lines (gate lines) GL extending in the horizontal line(row) direction.

The signal line drive circuits XD supply the image signals to the pixelelectrodes PE to be driven, with the signal lines (data lines) SLextending in the vertical line (column) direction. The signal lines SLare supplied with 1-bit video signals composed of binary digital data.The liquid crystal layer corresponding to each of the pixel electrodesPE is thereby driven to display in accordance with the image signals.

The above-explained specific circuit configuration of the display deviceis a mere example and is not limited to this. For example, theembodiment can be applied to, for example, what is called a touch-paneldisplay device incorporating a sensor electrode which detects a user'stouch operation by electrostatic capacitance.

The present invention is not limited to the embodiments described above,and the constituent elements of the invention can be modified in variousways without departing from the spirit and scope of the invention. Forexample, various aspects of the invention can also be extracted from anyappropriate combination of constituent elements disclosed in theembodiments. For example, some of the constituent elements disclosed inthe embodiments may be deleted. Furthermore, the constituent elementsdescribed in different embodiments may be arbitrarily combined.

What is claimed is:
 1. A display device comprising: a display unitconfigured to display an image for a right eye at a first position on ascreen and an image for a left eye at a second position on a screen,wherein a binocular parallax is in a range from 2 arc sec to 3 arc min,resolution of the display unit is P pixels or more per inch, a distancebetween the first position and the second position is between one pixeland 0.021×P pixels, P is 300, the display unit comprises sub-pixels ofred, green, and blue, two adjacent pixels in a first horizontal line arecomposed of six sub-pixels aligned in order of red, green, blue, blue,green, and red, and two adjacent pixels in a second horizontal lineadjacent to the first horizontal line are composed of six sub-pixelsaligned in order of red, red, green, blue, blue, and green.
 2. Thedisplay device of claim 1, further comprising: a memory configured tostore the image for the right eye and the image for the left eye; and acontroller configured to cause the image for the right eye and the imagefor the left eye to be read from the memory and to be displayed at thefirst position and the second position on the screen.
 3. The displaydevice of claim 1, further comprising: an optical element configured tocontrol propagation of light emitted from the display unit to make theimage for the right eye incident on an observer's right eye and to makethe image for the left eye incident on an observer's left eye.
 4. Thedisplay device of claim 3, wherein the optical element comprises alenticular lens, a parallax barrier, or a prism.
 5. The display deviceof claim 1, wherein a pixel of the display unit comprises sub-pixels ofdifferent colors, the display device further comprises: a prism arrangedfor the sub-pixels and configured to control a direction of lightemitted from each of the sub-pixels to make the image for the right eyeincident on an observer's right eye and to make the image for the lefteye incident on an observer's left eye, wherein a shape of the prism isdifferent for the sub pixels of different colors.
 6. The display deviceof claim 5, wherein the prism is formed of a material different inrefractive index in accordance with a wavelength of light, and the shapeof the prism corresponds to the refractive index to light emitted fromthe sub-pixels.
 7. A display device comprising: a display unitconfigured to display an image for a right eye at a first position on ascreen and an image for a left eye at a second position on a screen; anda prism, wherein a binocular parallax is in a range from 2 arc sec to 3arc min, resolution of the display unit is P pixels or more per inch, apixel of the display unit comprises sub-pixels of different colors, adistance between the first position and the second position is betweenone pixel and 0.021×pixels, P is 300, the display unit comprisessub-pixels of red, green, and blue, two adjacent pixels in a firsthorizontal line are composed of six sub-pixels aligned in order of red,green, blue, blue, green, and red, and two adjacent pixels in a secondhorizontal line adjacent to the first horizontal line are composed ofsix sub-pixels aligned in order of red, red, green, blue, blue, andgreen.
 8. The display device of claim 7, further comprising: a memoryconfigured to store the image for the right eye and the image for theleft eye; and a controller configured to cause the image for the righteye and the image for the left eye to be read from the memory and to bedisplayed at the first position and the second position on the screen.9. The display device of claim 7, further comprising: an optical elementconfigured to control propagation of light emitted from the display unitto make the image for the right eye incident on an observer's right eyeand to make the image for the left eye incident on an observer's lefteye.
 10. The display device of claim 9, wherein the optical elementcomprises a lenticular lens, a parallax barrier, or a prism.
 11. Adisplay device comprising: a display unit configured to display an imagefor a right eye at a first position on a screen and an image for a lefteye at a second position on a screen, wherein a binocular parallax is ina range from 2 arc sec to 3 arc min, resolution of the display unit is Ppixels or more per inch, a distance between the first position and thesecond position is between one pixel and 0.021×P pixels, P is 300, apixel of the display unit comprises sub-pixels of different colors, andthe display device further comprises: a prism arranged for thesub-pixels and configured to control a direction of light emitted fromeach of the sub-pixels to make the image for the right eye incident onan observer's right eye and to make the image for the left eye incidenton an observer's left eye, wherein a shape of the prism is different forthe sub pixels of different colors.